<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <script src="../react18/react.development.js"></script>
  <script src="../react18/react-dom.development.js"></script>
  <script src="../react18/babel.min.js"></script>
</head>

<body>
  <button id="btn">修改vDOM,并重新渲染</button>
  <div id="app"></div>
  <script type="text/babel">
    /* 
      diff算法的比较
        Diff算法比较只会在同层级进行, 不会跨层级比较,如果当前层级不一致则直接替换
        diff算法在某个层级比较一致的话,会进入层级内部再次比较,默认按照DOM书写顺序进行比较

        伪代码:
        旧的虚拟DOM
          <li key="html">html</li>
          <li key="css">css</li>
          <li key="js">js</li>

        新的虚拟DOM
          <li key="react">react</li>
          <li key="html">html</li>
          <li key="css">css</li>
          <li key="js">js</li>
  
  
    */
    // const arr = ["html","css","js","jq"]
    // const vDOM = (
    //   <ul>
    //     {
    //       arr.map((item,index) => (<li key={item}>{item}</li>))
    //     }  
    //   </ul>
    // )
    // const root = ReactDOM.createRoot(document.getElementById('app'));
    // root.render(vDOM)


    // //给按钮绑定点击事件,修改数据 然后重新得到新的vDOM 重新渲染
    // const oBtn = document.getElementById('btn');
    // let i = 0;
    // oBtn.onclick  = function(){
    //   arr.unshift("react" + i++);
    //   const vDOM = (
    //     <ul>
    //       {
    //         arr.map((item,index) => (<li key={item}>{item}</li>))
    //       }  
    //     </ul>
    //   )
    //   root.render(vDOM)
    // }

const arr=["html","css","js","jq"]
const vDOM=(
  <ul>
        {
         arr.map((item,index)=>( <li key={item}>{item}</li> ))
        }  
      </ul>
)
const root=ReactDOM.createRoot(document.getElementById("app"))
root.render(vDOM)

const oBtn=document.getElementById("btn")
let i=0
oBtn.onclick=function(){

arr.unshift("react"+i++)
const vDOM=(
  <ul>
          {
            arr.map((item,index) => (<li key={item}>{item}</li>))
          }  
        </ul>
)
root.render(vDOM)
}


  </script>
</body>

</html>